A quick question

My mallards are still kind of young and I'm trying to figure out if I have the sexs right based on what little I know. 2 are proudly quacking and the other one doesn't really do anything. The same 2 quacking have orange to a darker color bill, with the other 1 yellow. Are the 2 quacking hens and the one doing nothing a drake. Can all mallards quack at first then the drakes just kind of form a whistle? There young enough I cant see any green feathers forming. I'm hoping I end up with 2 hens and a drake, but if not I can always buy a couple more. What do you all think?